This one is so simple, yet so good. And you know it. Has to be in the collection.
Source Gluszczenko
Background formed from the original with an emboss effect
Source GDJ
From an image on opengameart.org shared by rubberduck.
Source Firkin
A seamless texture of black leather. I think it will look best when used in headers, footers or sidebars.
Source V. Hartikainen
Could remind you a bit of those squares in Super Mario Bros, yeh?
Source Jeff Wall
Feel free to use this seamless background texture as a background on a web site. It's colored in a light pink color and is seamlessly tile-able.
Source V. Hartikainen
Honestly, who does not like a little pipe and mustache?
Source Luca Errico
Tiny circle waves, almost like the ocean.
Source Sagive
The following free background pattern has glossy diagonal stripes as a texture to it, and it's colored in a light blue gray color. This background pattern is suitable for using in web design or any other graphic design projects. This applies to all background patterns here.
Source V. Hartikainen
Submitted as a black pattern, I made it light and a few steps more subtle.
Source Andy
Here's a dark background pattern that contains a steel grid pattern as a texture. Use it as a website background or for other purposes. It's free!
Source V. Hartikainen
Dark squares with some virus-looking dots in the grid.
Source Hugo Loning
Seamless , tileable CC-0 texture. Created by my own, feel free to use wherever you want!
Source Linolafett
Bright Multicolored Floral Background by Karen Arnold from PDP.
Source GDJ
The tile this fill pattern is based on can be had by using shift+alt+i on the rectangle.
Source Firkin
Inspired by a pattern seen on a public domain image of a very old tile. To get the unit cell, select the rectangle in Inkscape and use shift+alt+i.
Source Firkin
Actually remixed from a pattern on Pixabay. But then noticed a very similar one on Openclipart.org uploaded by btj51q2.
Source Firkin
Very dark pattern with some noise and 45-degree lines.
Source Stefan Aleksić
Prismatic Abstract Geometric Background 5 No Black
Source GDJ
A seamless pattern of "sewn stripes" colored in light gray.
Source V. Hartikainen